KUALA LUMPUR, March 13 (Reuters) - One of the world's most perplexing aviation mysteries is casting a harsh spotlight on Malaysia's government, as a leadership unused to heavy scrutiny comes under intense international criticism for a litany of confusing messages and a perceived lack of transparency.

Five days after Malaysia Airlines flight MH370 disappeared from civilian radar screens, a huge international search operation has failed to turn up a trace of the Boeing jetliner that was carrying 239 passengers and crew.

Frustration over the fruitless search has increasingly been directed at Malaysian officials after a series of fumbling news conferences, incorrect details given by the national airline, and a long delay in divulging details of the military's tracking of what could have been the plane hundreds of miles off course.

The missteps have ranged from conflicting information about the last time of contact with the jet to the sharing of photos of two passengers in which they had the same pair of legs.

"The Malaysians deserve to be criticized - their handling of this has been atrocious," said Ernest Bower, a Southeast Asia specialist at the Center for Strategic and International Studies in Washington.

Government officials say they are coping as best they can with an exceptional, highly complex crisis.

Confusion, false leads, and misinformation are common in the initial hours of air disasters in any country.

But China, whose citizens made up around two-thirds of the passengers on board the flight, has barely hidden its impatience with Malaysia, urging it several times to step up the search and investigation efforts.

The head of the Civil Aviation Authority of China, Li Jiaxiang, told reporters on Thursday that the message had been repeated to Malaysia's special envoy in the Chinese capital.

"Yesterday Malaysia's special envoy arrived in Beijing, and the CAAC asked of him that Malaysia step up search efforts and increase their scope, and that we hope that Malaysia's information release and communication can be smoother," he said.

FAMILIES ANGRY

Some families of the up to 154 missing Chinese have voiced fury at what they said was the slow release of information. Verbal abuse and water bottles were hurled at representatives of the government-owned airline in Beijing.

"The core of Malaysia's information hasn't been consistent from start to finish," said China's widely read and influential Global Times tabloid, published by the Communist Party's official People's Daily.

"It certainly hits at the confidence that the rest of the world has in Malaysia's ability to be the nucleus of the rescue mission," the paper added.

Other governments have praised the Malaysian effort, but some officials have complained of a lack of communication and information sharing that has slowed initial fact-finding.

U.S. officials said Malaysia's failure to disclose the military's radar tracking data until days after the plane's disappearance meant important evidence may have disappeared.

"The lack of communication about what is going on is catastrophic," said one Western regulatory source, asking not to be identified. "We are in the fourth dimension here."

COMMUNICATION DEFICIT

Malaysia's government, one of the longest-serving in the democratic world with the same coalition in power for the 57 years since independence, has struggled to cope with the harsh glare of international scrutiny.

The ruling United Malays National Organisation has long been criticised, including by some of its own members, for cronyism, an authoritarian streak and breeding a political culture in which loyalty is prized over talent.

Majority ethnic Malays have benefited from a system of economic and social privileges that has steadily alienated ethnic Chinese and Indians, who make up large minorities in the nation of 29 million people.

Just a day before the plane vanished, a court convicted opposition leader Anwar Ibrahim of sodomy and sentenced him to five years in prison, overturning his acquittal two years ago in a ruling that supporters and international human rights groups say was politically influenced.

Ministries often meet requests for information or interviews with silence.

"There was a lot of confusion on the first and second days of this incident," a senior Malaysian defence official with knowledge of the operations told Reuters.

"A lot of permissioning, especially when you start sharing information with other ministries in government. I admit there is a lot of bureaucracy and we were slow."

Malaysia's response has been overseen personally by Prime Minister Najib Razak, who put his cousin - the defence and acting transport minister Hishammuddin Hussein - in charge of day-to-day operations and interaction with the media.

"This is unique what we are going through," Hishammuddin told reporters at a Wednesday news conference, batting away their complaints over a lack of transparency. "Coordinating with so many countries is not easy."

The frequency of news conferences given to hundreds of reporters now massed at a hotel next to the international airport has dwindled sharply since the first day. The delayed briefing on Wednesday evening was the first to give details on the search operation in two days.

CONFUSION FROM START

The confusion began hours after the flight vanished from air traffic control radar early on Saturday morning. Malaysian Airlines initially said the plane lost contact at 2:40 a.m., two hours after its departure. Hours later, it corrected the time to 1:30 a.m.

As details emerged that some passengers had boarded the flight using stolen passports, Malaysia's home minister was quoted by state news agency Bernama as saying that two men travelling on Italian and Austrian documents had "Asian faces".

That was denied by Hishammuddin, and the muddle deepened when Malaysia's aviation chief attempted a confusing analogy with the black Italian footballer Mario Balotelli.

The men turned out to be Iranians who were not suspected of being connected with the disappearance of the plane.

On Tuesday, police displayed pictures of the two in which their legs appeared exactly the same, sparking speculation of a cover-up. Police later said this was a photocopying error, according to local media.

National police chief Khalid Abu Bakar flatly denied a statement by the aviation chief that there were five passengers who checked-in for the flight and did not board. Malaysia Airlines later clarified there had been four passengers who did not show up at the airport for the flight.

Perhaps the greatest confusion was generated by the Malaysian military's revelation on Sunday that the plane may have turned back from its scheduled path off Malaysia's east coast before disappearing.

Officials did not give more details on the suspected "turnback" until Wednesday, leaving a gap that was filled by speculation the government was hiding something and doubts over whether the search was being conducted in the right place.

On Wednesday, officials confirmed they tracked an unidentified aircraft into the Malacca Strait, hundreds of miles and off the opposite coast from where the jet went missing.

Bowers, the Southeast Asia specialist, said Malaysia's apparent mishandling of the situation could have long-term strategic consequences in a region where China's economic and military might is growing rapidly.

"They have no maritime domain awareness and it doesn't look like they have a strong command and control structure and they're not well coordinated with friends. Sadly, that's what the MH370 situation demonstrates," he said of Malaysia.

"It's not good and it fits in with the narrative I believe is forming in Beijing that China should and needs to take control." (Additional reporting by Niluksi Koswanage, Al-Zaquan Amer Hamzah and Yantoultra Ngui in Kuala Lumpur, Ben Blanchard in Beijing,; Tim Hepher in Paris,; Andrea Shalal-Esa and David Brunnstrom in Washington; Editing by Alex Richardson and Nick Macfie)